Desiccators



Dec. 6, 196 6 c, H WILLIAMS 3,289,879

DESICCATORS Filed Jan. 26, 1965 3,289,879 DESICCATGRS Claude HubertWilliams, Chalfont St. Peter, England, assignor to Jencons (Scientific)Limited, Hertfordshire, England, a British company Filed Jan. 26, 1965,Ser. No. 428,145 Claims priority, application Great Britain, Jan. 27,1964, 3,362/ 64 1 Claim. (Cl. 220-46) This invention relates todesiccators which are particularly, although not exclusively, used fordrying materials nnder vacuum in laboratories.

The conventional desiccator consists of a deep round bowl, oftenfrusto-conical in shape, having a broad flange formed around the upperpart, the flange having a finely ground plane upper surface. The coverconsists of a deeply domed, roughly hemi-spherical, part having asimilar broad flange formed around its base to mate with the flange onthe bowl. The flange of the cover is also carefully ground on its underside to a plane surface. In use the bowl is charged with the material orobjects to be dried and the cover is then placed on the bowl so that thetwo plane flange surfaces are in contact, a layer of grease being placedbetween the two surfaces. There is a vacuum connection at the top of thecover and when a vacuum is applied the external atmospheric pressureforces the two flanges into firm contact to provide, with the aid of thefilm of grease, a vacuum-tight joint.

This conventional type of desiccator has numerous disadvantages.Firstly, it is necessary to produce the finely ground plane surfaces onthe two flanges and this is a comparatively slow and costly operation.Furthermore, the ground surfaces have to be carefully protected fromchipping or other damage which can impair the vacuum seal. If thedesiccator has been under vacuum for a considerable time the cover maybe very difficult to remove because the two plane surfaces are in suchtight and intimate contact, and if an attempt is made to introduce atool between the surfaces to prise them apart damage may very easilyoccur. The broad, projecting flanges are, of course, easily subject todamage, for example, by having pieces broken out of them while in storeor while being loaded or unloaded.

When loading the desiccator it is, of course, essential to ensure thatno particles of grit or other foreign matter are picked up by thegreased flange surfaces and extremely careful handling is, therefore,necessary.

The principal object of the invention is to avoid these difficulties byeliminating the ground flanges on the desiccator bowl and its cover.

According to the invention, a desiccator comprises a bowl and a coverhaving corresponding annular joint surfaces, one of the surfaces beingprovided with a circular' groove and the other being provided around itsouter periphery with a shallow projecting stepped portion, and a ringseal, such as an O-ring, in the groove.

Preferably the groove is tapered so that the mouth is wider than thebottom thereof.

The bowl of the desiccator may also be provided with a substantiallysemi-circular groove around its outer periphery, in which a secondresilient ring is disposed, to protect the desiccator from damage due tostriking other hard objects.

In order that the invention may be clearly understood and readily put topractical use, one embodiment there- United States Patent "ice of willnow be described, by way of example, with reference to the single figureof the accompany drawing.

Referring to the drawing, which shows only a part of a desiccator withthe upper portion of the bowl and the lower portion of the cover insection, the bowl has a wall 11 which is considerably thickened at theupper portion 12. The thickened wall portion 12 has a fiat upper annularsurface 13, and contained in the upper surface 13 is a groove 14 whichis of tapered form, that is to say, the mouth of the groove is widerthan the bottom thereof. Seated in this groove is a ring seal or O-ring15 which is preferably of such cross-sectional diameter that when placedin the groove 14 it seats itself in the mouth of the groove and cannotsettle in the bottom thereof.

The cover of the desiccator, which may be of the usual deeply domedshape with a vacuum connection at its top, has a wall 16 of appropriatethickness and a thickened portion 17 around its opening, the wallportion 17 terminating in an annular lower face 18 which is providedaround its periphery with a shallow projecting stepped portion 19.

As shown in the drawing, the bowl and the cover are slightly separated,but it will be evident that when the cover is pressed down on to thebowl, and more especially when vacuum is subsequently applied, the coverwill descend on to the bowl until the outer surface of the steppedportion 19 is in contact with the upper surface 13 of the bowl, and asthe bowl is pressed into position the seal 15 is forced more deeply intothe groove 14. At the same time, the upper portion of the ring seal 15is flattened to conform to the surface 18. Thus the seal, whencompressed, will have three flattened portions formed around it, two ofthem mating with the walls of the groove 14 and the third conforming tothe surface 18. This provides an extremely effective vacuum seal whichremains completely vacuum tight for long periods. On the other hand, assoon as the vacuum is released, the natural resilience of the seal 15tends to push the cover upwardly and, in any case, since the uppersurface 13 and the outer surface of the step 19 are not greased, it is avery easy matter to separate the cover from the bowl. The necessity toforce the cover away from the bowl is entirely avoided so that objectsor powders contained in the desiccator bowl are not rattled about orupset in the process.

In addition it should be noted that the provision of the stepped portion19 ensures that the cover, when in contact with the surface 13 of thebowl, flattens the O evenly, and overcomes any tendency of the cover tocompress the O ring unevenly if the latter was softer in certain parts.

Further advantages derived from the invention are that, since there areno greased surfaces, the possibility of picking up grit or other foreignmatter on the sealing surfaces is virtually eliminated, and that thesealing ring itself may easily be replaced from time to time.

As a further protection for the desiccator, either when in store withother glassware or with hard metal apparatus, or when in use on thelaboratory bench, it is protected against accidental damage by theprovision of a further resilient ring 20, held in a part-circularperipheral groove. The ring 20 may conveniently be a ring seal similarto the seal 15 but of a larger size. A further ring similar to the ring20 may also be provided in the cover, or if desired in both bowl andcover.

I claim:

A desiccator to be evacuated of air comprising a bowl and a cover havingcooperiing annular flanges, one of References Cited by the Examiner ifiiifiii rii ii er iii iiil i iiiiiiii gfii gie irl UNITED STATES PATENTSsaid groove and projecting above the surface of said 1759176 5/1930Voorhees 2151OO'5 flange, the other flange being provided around itsouter 5 2751123 6/1956 KPhles et a1 220 550 periphery with a projectingstepped portion for abutting with the surface of said one flange whensaid desiccator is evacuated, said stepped portion being of such aheight as to limit the deformation of said O-ring whereby said THERONCONDON Prlmary Exammer' O-ring is evenly compressed between said otherflange and 10 LOUIS MANCENE, JAMES MARBERT,

said tapered Walls to form an airtight seal. xami e s.

